In a written message distributed to the employees at noon, E. Douglas Sargent, president of Lockheed Space Operations Co., stated that most of the company's normal shuttle-processing work will resume shortly. He did not elaborate on the changes.

''We will not be performing certain operations, and work will be scheduled to avoid overtime,'' Sargent's letter read. ''The findings of the investigation may dictate changes in our normal processing operations.''

Lockheed spokesman John Williams said he did not know what operations were being ceased. He said the company's major focus will be supporting NASA's investigation into Tuesday's fatal shuttle launch but that processing of flight hardware would continue. ''We are at work,'' he said.

A Lockheed technician, who would speak only on the condition that he remain anonymous because of fear of losing his job, said work at Lockheed the past three days has been mostly cleanup, inspections and paper processing. Employees were frustrated, he said, because they knew so little about their futures. Supervisors had said an announcement might be made Monday.

But Lockheed officials, like those in other companies who have shuttle contracts, said NASA determines their tasks, and NASA has sent no word yet to alter their routines.

As of Thursday, McDonnell Douglas employees were continuing to test and check the Spartan observatory that was to have been released from the shuttle Columbia in March to study Halley's comet. Martin Marietta Aerospace was manufacturing the shuttles' external fuel tanks in New Orleans. And at the Morton Thiokol Inc. Wasatch Operations in Brigham City, Utah, the shuttle's solid rocket boosters were moving down the assembly line.

''We know we are going to have to stop making them at some time,'' Morton Thiokol spokesman Rocky Raab said. ''If they don't use them, you have to stop making them.''